Fuel container

ABSTRACT

The invention concerns a fuel container of plastic material such as a motor vehicle fuel tank, comprising one or more welded seams as seam locations for the body of the container and/or as connecting or sealing seams between the container wall in the region of openings and closure elements or covers welded thereto. At least some of the welded seams are at least partially penetrated by a duct which extends in the longitudinal direction in the seam and which can be filled with air and vented.

FIELD OF THE INVENTION

[0001] The invention relates generally to a fuel container of plasticmaterial and more particularly a fuel container in the form of a fueltank of plastic material, for example for a motor vehicle.

BACKGROUND OF THE INVENTION

[0002] A typical form of a fuel container of plastic material comprisesone or more welded seams acting as seam locations for affordingstructural integrity of the container body and/or in the form ofconnecting or sealing seams between a wall portion of the container bodyin the region of openings therethrough and closure elements or coverswhich are thereby secured to the container body. There is a wide rangeof different design configurations of fuel containers of that kind, forexample as motor vehicle fuel tanks, which substantially comprisepolyethylene. Such fuel containers of plastic material are to a greateror lesser degree permeable in relation to hydrocarbons, and, in the caseof containers consisting of a single layer of polyethylene, hydrocarbonscan fairly readily diffuse through the wall of the container.

[0003] A level of permeability which is markedly reduced in comparisonwith single-layer fuel containers or tanks of polyethylene is achievedin the case of fuel containers which are of a multi-layer wallstructure, with diffusion-type barrier layers incorporated therein. Suchcontainers are predominantly produced by an extrusion blow moldingprocedure. However even such containers may not be completely gas-tight.Problems arise in connection with such containers in relation toconnecting elements such as valves and nipples which may necessarily beprovided on the container, as well as the welded seams, through whichhydrocarbons can still diffuse, as in the region of the welded seams thebarrier layers are not directly welded to each other but in very thinresidual layers are separated by material which has little barriereffect.

[0004] This problem is already addressed in WO 00/48859. To resolve thatproblem, it is proposed therein that a fuel tank is provided with acover of a hood-like configuration, which forms, between itself and theouter wall surface of the tank, a cavity which is in the form of a fuelvapor collecting chamber and which encloses the seams of the tank aswell as various connecting openings and cover members thereon. Thathood-like cover is connected by welding to the outside wall surface ofthe tank. Such a structure is extremely complicated and expensive and inaddition such a design configuration still allows hydrocarbons to bedischarged to the ambient atmosphere through the welded seams of thehood-like cover.

[0005] Consideration may also be given to DE 198 53 097 A1 disclosingfor example a fuel container or tank which is composed of two halves andwhich has a wall produced from plastic material by an injection moldingprocedure. Each half of the tank in turn comprises shell portions whichare arranged in mutually superposed relationship and between which aslit or gap is left free. Fuel vapors which have passed into that gapare removed therefrom and filtered. Such a design configuration stillinvolves the problem that the welded seams of the tank representpotential weak points.

SUMMARY OF THE INVENTION

[0006] An object of the present invention is to improve a fuel containerof plastic material, such that it discharges as little fuel vapor to theambient atmosphere as possible.

[0007] Another object of the present invention is to provide a fuelcontainer of plastic material which, while affording appropriatestructural integrity, can satisfy demands made thereon in terms ofemission of fuel vapors to the atmosphere, without entailing a complexdesign configuration.

[0008] Still another object of the invention is to provide a fuelcontainer of plastic material, so designed as to avoid serious fuelvapor emissions to the ambient atmosphere without involving majorstructural steps for completely sealing off welded seams of the fuelcontainer.

[0009] In accordance with the principles of the present invention theforegoing and other objects are attained by a fuel container of plasticmaterial, for example a motor vehicle tank, comprising one or morewelded seams as seam locations of the container body and/or asconnecting or welding seams between a wall of the container body in theregion of at least one opening and a closure element or cover weldedthereto. At least one of the welded seams is at least partiallypenetrated by a duct which extends in the longitudinal directionthereof. The duct can be filled with air and vented of air forventilation purposes.

[0010] As will be seen in greater detail from preferred embodiments ofthe invention as described hereinafter instead of requiring total andcomplete sealing of the welded seams of the container, which can beachieved only at the cost of extremely high structural complication andexpenditure, in general terms, the invention aims to provide forventilation of the welded seams by means of the duct passingtherethrough, which can be implemented using simple means.

[0011] In a preferred feature of the invention the duct can haveconnections for filling and venting, at each end.

[0012] In a further preferred feature the connections can be providedwith valves, for example for air-filling or venting purposes.

[0013] In the case of a fuel container which was produced by extrusionblow molding from a multi-layer preform, a preferred feature can providethat the duct was produced by recesses or openings in the edges of theblow molding mold.

[0014] When the fuel container is made from two half-shell portionswhich are welded together, with the half-shell portions beingrespectively welded together at connecting flanges thereon, theconnecting flanges can each have groove-shaped openings forming at leastone duct.

[0015] As an alternative thereto the fuel container can be formed fromtwo half-shell portions which are welded together at their ends, with atleast one duct being kept free between two peripherally extending stepsor shoulders of the half-shell portions.

[0016] In a further preferred feature of the invention the seam locationof the container body, which includes a respective duct, can bepenetrated in a portion-wise manner by the duct, wherein a plurality ofduct portions can communicate with a common venting conduit. Venting ofat least one duct can be effected by way of a filter element, preferablyby way of an activated carbon filter which is in any case associatedwith the fuel container.

[0017] Finally, means can be provided for pressure filling at least oneduct with air. The flushing air which is introduced into the duct inthat way can be passed to the internal combustion engine which is fedwith fuel from the fuel container, or to an activated carbon filterwhich is in any case present in a motor vehicle. Ventilation of thepassages can be effected both by means of a reduced pressure and also bymeans of an increased pressure.

[0018] It will be assumed however that the introduction of air willautomatically occur by virtue of the drop in concentration of thehydrocarbon vapors, in a duct according to the invention, when that ductfor example is connected to a filter element.

[0019] Further objects, features and advantages of the invention will beapparent from the description hereinafter of preferred embodimentsthereof.

BRIEF DESCRIPTION OF THE DRAWING

[0020]FIG. 1 is a perspective view of a fuel container of plasticmaterial, in the form of a motor vehicle tank,

[0021]FIG. 2 is a view on an enlarged scale in section of a welded seamon a blow-molded fuel container of plastic material, which is structuredin known manner and thus represents state of the art,

[0022]FIG. 3 shows a portion on an enlarged scale of the wall of a fuelcontainer as shown in FIG. 2,

[0023]FIG. 4 is a view in section through part of a fuel container inaccordance with a first embodiment of the invention in the region of awelded seam,

[0024]FIG. 5 is a simplified view on to the welded seam shown in FIG. 4,

[0025]FIG. 6 is a partial section through a blow molding mold showingproduction of a fuel container in accordance with the first embodimentof the invention,

[0026]FIG. 7 is a view in section on an enlarged scale through the wallof a fuel container in accordance with a second embodiment of theinvention in the region of a welded seam, this fuel container beingcomposed of two half-shell portions,

[0027]FIGS. 8 through 11 show various configurations of a connectionbetween two half-shell portions to constitute a fuel container, and

[0028]FIGS. 12 and 13 are views in section on an enlarged scale of apart of the wall of a fuel container.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Referring firstly to FIG. 1, shown therein is a greatlysimplified perspective view of a fuel container 1 of plastic material,which has a peripherally extending welded seam generally indicated at 2.The fuel container 1 shown can typically be the fuel tank of a motorvehicle.

[0030] The illustrated fuel container 1 is preferably in the form of ahollow molding produced by extrusion blow molding, with a multi-layercontainer wall as indicated at 3 in FIG. 2, which in known mannerinvolves a six-layer structure including an inwardly disposed barrierlayer 4 to afford permeability resistance for hydrocarbons.

[0031] It should be mentioned at this juncture that the inventionexpressly also concerns fuel containers which were welded together fromtwo half-shell portions in the second heat. Whether the plasticcomponents to be welded together are of a single-layer or multi-layerstructure is of significance in regard to the invention only insofar asthe problem of the welded seams as potential diffusion weak points inthe fuel container is important, in particular in the case of fuelcontainers with walls of a multi-layer structure.

[0032] These problems will be discussed hereinafter with reference toFIGS. 2 and 3, with FIG. 2 showing part of a container wall 3 with awelded seam 2 formed by the procedure in the state of the art.

[0033]FIG. 3 shows a portion on an enlarged scale from the containerwall 3 in FIG. 2, showing the typical structure of a multi-layercontainer wall 3 of a plastic container produced by extrusion blowmolding. The wall comprises an outer layer 5 and an inner layer 6, eachcomprising polyethylene. The outer layer is possibly of a dark color.The outer layer 5 is of a layer thickness of between about 10 and 15% ofthe overall thickness of the container wall and the inner layer is of athickness of about 20%, as the load-bearing layer. Reference 7 denotes alayer of regenerated or recycled material, for example processed wastematerial or scrap, generally comprising a mixture of all materialsforming the container wall 3. The barrier layer 4 is embedded betweenthe layer 7 and the inner layer 6, with the interposition of bondinglayers.

[0034] It will be appreciated that, upon production of a fuel container1 of such a configuration by extrusion blow molding the operation ofsqueezing off the tubular preform will give rise to a welded seam 2 ofgreater or lesser size and which under some circumstances may extendcompletely around the fuel container, as is shown in FIG. 2. As canreadily be seen from FIG. 2 it will be appreciated that the inner layers6 of the container wall 3 in that case bear against each other. In theregion of the location where the tubular preform is squeezed off, allthe layers blend together, but over wide parts of the welded connectionformed in that way only the inner layers 6 of adjacent wall regions arein contact against each other, even if in that region they are of areduced residual thickness. Those residual-thickness layers have a lowerlevel of barrier effect in relation to hydrocarbons so that consequentlya small proportion of hydrocarbons can still diffuse through the weldedseam 2.

[0035] Reference is now made to FIG. 4 showing an embodiment of a weldedseam of a fuel container 1 in accordance with the present invention. Thewelded seam 2 is of such a configuration that it is penetrated in itslongitudinal extent by a duct 10 which is adapted to be filled with andemptied of air. Hydrocarbons which diffuse from the interior of the fuelcontainer 1 through the inner layers 6 which are welded together andbetween the barrier layers 4 pass into the duct 10 by virtue of thelower partial pressure therein.

[0036] It will be noted that the wall structure of the fuel container isshown in simplified views in the relevant Figures illustrating thevarious embodiments of the invention, and that wall structure shouldapproximately correspond to that illustrated in FIG. 3.

[0037] Looking now at FIG. 5, the view therein diagrammatically showsthat the duct 10 is provided at each of two end positions with anair-filling or intake connection 11 and an air-discharge or ventingconnection 12. By virtue of a drop in concentration in the duct 10 to afilter element (not shown), fuel vapors will be positively caused toflow through the duct 10 and issue therefrom into the filter element. Itwill be noted that the duct 10 can also be specifically and targetedlyflushed with air or ventilated, for example either by applying a reducedpressure to the duct at an appropriate location or by applying anincreased pressure thereto. The flushing air does not necessarily haveto be fed to a filter element but rather it can also be fed to thecombustion air for the associated engine.

[0038] The connections 11 and 12 which are provided for ventilationpurposes on the duct 10 can also be formed in the procedure forproducing the fuel container 1.

[0039] Reference is now made to FIG. 6 diagrammatically showingmanufacture of a fuel container 1 in accordance with the presentinvention by extrusion blow molding. In FIG. 6, references 13 a and 13 bshow first and second mold portions of a blow molding mold in a closedcondition, while reference 14 denotes cutting edges which sever thematerial, projecting out of the mold, of the preform which is alreadyexpanded under the effect of an increased pressure therein, thereby toform the welded seam 2. As can be seen from FIG. 6 the squeeze edges ofthe mold portions 13 a, 13 b are each provided with a respectivesemicircular groove 15 which extends around the mold. The grooves 15form a duct-shaped opening or recess when the mold portions 13 a, 13 bare in the closed condition as shown. In order to ensure that the duct10 remains free and open and the walls of the container are not weldedtogether in that region, a plurality of blowing needles 16 which arearranged at spacings in succession may possibly be provided in thelongitudinal direction of the welded seam 2, for example at least at thebeginning and at the end of the duct 10. The blowing needles 16 extendinto the opening or recess defined by the grooves 15 and serve tointroduce blowing air thereinto in order to cause the duct 10 to beinflated into the appropriate shape against the wall surfaces of thegrooves 15.

[0040] Looking now at FIG. 7, diagrammatically shown therein is aconnection on a fuel container 1 comprising two prefabricated half-shellportions 17 each of a multi-layer wall structure. The regions which areto be welded together are each in the form of peripherally extendingflange-like collars 18. A duct 10 of the kind described hereinbefore isalso formed by channels 19 which are provided in the respective collars18, after the two half-shell portions 17 are welded together.

[0041]FIGS. 8 through 11 show various alternative configurations ofcontainer walls 3 when first and second half-shell portions 17 arewelded together to form a fuel container 1. In the alternativeconfiguration of the wall container 3 in the region of the welded seam2, as shown in FIG. 8, the inside wall of the first half-shell portion17, being the upper half-shell portion in FIG. 8, is welded to theoutside wall of the second half-shell portion 17, thereby forming theduct 10 therebetween. In this configuration of the connection betweenthe half-shell portions 17, pressure can be applied to the welded seam 2at the inside of the container when making the connection, such pressurebeing produced for example by means of a gaseous medium.

[0042] In the case of the connection shown in FIG. 9 the container walls3 are welded together in the manner of an end butting relationship,forming respective steps or shoulders as indicated at 20. For thepurposes of centering the half-shell portions 17 with respect to eachother and in order to keep the duct 10 open, spacers in the form ofrespective knobs 21 are provided at the inside and outside on the wallregions of the half-shell portions 17, which form the duct 10. The knobs21 are arranged in respective rows which extend in the longitudinaldirection of the welded seam 2, and thus into the plane of the drawing.

[0043] In the case of the connection between the half-shell portions 17as shown in FIGS. 10 and 11, one half-shell portion 17 is of aconfiguration such as to conically enlarge in a direction towards itsopening, in other words, the upper half-shell portion 17 in FIG. 10expands conically outwardly in a downward direction, whereas the otherhalf-shell portion, being the lower half-shell portion 17 in FIG. 10, isof a conically inwardly tapering configuration in complementaryrelationship therewith, thereby affording an angular position for thewelded seam or seams 2, which is such that it can compensate forinaccuracies in respect of shape and in which a pressure is applied tothe welded seam 2 when the half-shell portions 17 are fitted together.

[0044] It will be appreciated that while the foregoing text at theappropriate locations refers in each case only to a welded seam, that isalso intended to denote first and second welded seams which are at aspacing from each other, being separated by the duct 10.

[0045] Finally, referring to FIGS. 12 and 13, shown therein is thewelding of a multi-layer cover 22 with at least one barrier layer 4embedded therein, to the container wall 3, in the region of an opening23 therein. Provided in the cover 22 on the inward face thereof, that isto say on the face thereof which is towards the container wall 3,extending peripherally therearound at the edge portion thereof, is achannel 19 which is of semicircular cross-section and which forms a ductwhich is also Semicircular in cross-section. A corresponding channel isnot provided in the container wall 3 as that is not absolutely necessaryand would only represent unnecessary weakening of the container wall 3in that region. It will be appreciated that in a corresponding mannerthe duct may also be of the configuration shown in the embodiments ofFIGS. 7 through 11. FIG. 13 shows an alternative form of this structurewhere a cover 22 is welded to the fuel container in the region of anopening 23, at a location where the container wall 3 forms a coverflange or neck structure 24. FIG. 13 also shows an air intake connection11 communicating with the duct 10 and an air-discharge or ventingconnection 12. It will be appreciated that the connections 11 and 12 mayalso be provided in the embodiment illustrated in FIG. 12 but are notshown therein.

[0046] It will be appreciated that the above-described embodiments ofthe invention have been set forth solely by way of example andillustration of the principles of the present invention and that variousother modifications and alterations may be made therein without therebydeparting from the spirit and scope of the invention. For example theshell portions 17 may be obtained by cutting open a blow-moldedcontainer or tank.

What is claimed is
 1. A fuel container of plastic material comprising acontainer body having at least one welded seam, a duct which at leastpartially penetrates at least one welded seam and extends in alongitudinal direction of the welded seam, and means for filling theduct with air and venting same of air.
 2. A fuel container as set forthin claim 1 wherein the welded seams are seam locations of the containerbody.
 3. A fuel container as set forth in claim 1 wherein the containerbody has at least one opening and a cover and wherein the welded seamsare connecting seams between a wall of the container body in the regionof the at least one opening and the cover.
 4. A fuel container as setforth in claim 1 wherein the container body has at least one opening anda closure element, and wherein the welded seams are connecting seamsbetween a wall of the container body in the region of the at least oneopening and the closure element.
 5. A container as set forth in claim 1wherein the duct has respective end portions and said means of the ductare respective connections at the end portions of the duct.
 6. Acontainer as set forth in claim 5 wherein the connections are providedwith valves.
 7. A container as set forth in claim 1 which is of amulti-layer structure having at least one barrier layer forhydrocarbons, which is completely embedded in the container body wall.8. A container as set forth in claim 1 which was produced by extrusionblow molding of a multi-layer preform, having a wall in which at leastone barrier layer for hydrocarbons is completely embedded, wherein theduct was formed by openings in squeeze edges of the blow molding mold.9. A container as set forth in claim 1 produced from first and secondshell portions which are welded together, wherein the shell portions arerespectively welded together at connecting flanges, and wherein at leastone connecting flange has at least one groove-shaped opening forming theduct.
 10. A container as set forth in claim 1 produced from first andsecond shell portions welded together, wherein the shell portions arerespectively welded together at connecting flanges, in each of which areprovided in pairs groove-shaped openings forming the duct.
 11. Acontainer as set forth in claim 1 produced from first and second shellportions welded together at their ends, wherein the shell portionsdefine first and second peripherally extending steps and at least oneduct is kept free between the steps of the shell portions.
 12. Acontainer as set forth in claim 9 wherein the shell portions wereobtained by cutting open a blow-molded container.
 13. A container as setforth in claim 1 wherein the seam of the container body is respectivelypenetrated in a portion-wise manner by a duct, and further including acommon venting conduit communicating with a plurality of duct portions.14. A container as set forth in claim 1 and further including a filterelement operatively associated with at least one duct for filteredventing thereof.
 15. A container as set forth in claim 14 wherein saidfilter element is an activated carbon filter operatively associated withthe container.
 16. A container as set forth in claim 1 and furtherincluding means for pressure filling at least one duct with air.